It has long been known that hydrogen (H2) is a plentiful and clean fuel for vehicles; the problem has always been how to load and store the highly volatile gas. But a new storage solution developed by the Helmholtz Center for Materials and Coastal Research (HZG) in the northernmost German state of Schleswig-Holstein could remove this barrier to market.
Hydrogen is a powerful mobility solution which is CO2-neutral and wholly renewable - it can be generated from wind power, methane and biomass, for example. When H2 is combined with oxygen in a fuel cell, energy in the form of electricity is produced plus water. Its use in vehicles has been limited by the fact it is expensive and technically complicated to load into tanks and to store. In today’s fuel cell vehicles (FCV), H2 is filled into compressed tanks at high pressures of up to 700 bar.
HZG’s solid fuel storage concept – the result of years of research – uses so-called magnesium hydrides (magnesium–nitrogen based) to capture the gas. The system has a number of advantages: the gas can be loaded up to five times faster and the tanks can store far more of it, providing more energy for volume. A magnesium hydride tank requires a volume of 46 litres to store 5kg hydrogen (which will carry an FCV c.500 km) compared to a high-pressure tank which requires 122 litres.
Until now, it would take 30 minutes to refuel magnesium hydride systems with 5kg of H2. But a doctoral student at HZG, Gökhan Gizer, found that by introducing nanoparticles of potassium-lithium titanate into the system, the tanks can be loaded quickly at a working temperature of below 180°C. "We have invented a system that makes the refuelling process about five times faster,” says Gizer, talking to Nature Scientific Reports, explaining how nanoparticles act as catalysts, binding the H2 atoms and accelerating loading.
The ‘nanotechnology’ team at HZG are now working on optimizing the kinetic behaviour of these materials to enable use in conventional vehicles and filling stations. "The results of this study take us a big step further towards competitive storage systems," explains the group leader Dr. Claudio Pistidda while talking to Nature Scientific Reports.